It is recognized that if carbon dioxide is brought into contact with liquid and mixed extensively over a long period of time or in a relatively large scale apparatus, it is possible to produce a satisfactory carbonated liquid. However, proper carbonation of the liquid becomes more difficult where a relatively small scale apparatus is used and where the carbonator is to occupy a relatively small space, for example in a drink dispensing machine in which the liquid is carbonated before use.
It is known, for example as disclosed in U.S. Pat. Nos. 1,945,489; 2,072,350; 2,201,430; and 3,851,797, to provide a diffuser type carbonator in which carbon dioxide gas is introduced inside a tubular or sleeve shaped micro-porous body which diffuses the carbon dioxide gas into a stream of liquid flowing over the outer side of the micro-porous body.